403 
approximate collections show this agreement. A comparison 
of Plates X., XXVII., and XXXI. with XXXVII., will ‘show 
that much of this disagreement is due to slight variations in the 
positions of the apices of the several pulses in the different 
localities. In each locality we can trace three diminishing 
pulses in this period, pulses, moreover, which have much in 
common, barring variations in amplitude and time of culmi- 
nation. Their similarity is greater than the 58 per cent. of agree- 
ment would seem to indicate. 
The most marked difference between the production in the 
river and in Thompson’s Lake, as has been shown, lies in the 
amplitude of the pulses, which in the river never attain the 
height that they do in the lake. A part of this contrast is due 
to the fact that pulses of production are sometimes flushed out 
by floods in the channel while they continue to a normal cul- 
mination in lake waters, as, forexample, the vernal pulse which 
culminates in the lake May 2. Similarly, in the flood of the last 
of Mayand July the plankton content is suddenly depleted in the 
channel waters, while the rising pulse continues to alaterand 
much higher culmination in the lake. 
1897. 
(Table VIIL, XIII; Pl. XXXVIII., L.) 
There are 18 collections in this year,at monthly intervals 
till July, and thereafter approximately every fortnight. The 
average annual production this year, 10.43 cm. per m.* is the 
largest recorded for this body of water, and is due to the exces- 
sive development in the low-water period, August-November, 
which reached an amplitude (35.35) over threefold that de- 
tected in the vernal pulse (10.58). (Pl. XX XVIII.) 
The hydrographic conditions are very different from those 
of the previous year, and change profoundly the relationship 
of the lake and river. As will be seen on Plate XXXVIIL., the 
river levels were above 6 ft. from the beginning of the year 
until June 6, and thereafter from the 25th until July 15,a total 
of 175 days in which the lake received water through the 
